Determine the truth vale of each of these statements if the
     Determine the truth vale of each of these statements if the domain of each variable consists of all integers.  x  y(x + 4 = y)  x  y(x - y = y - x)  x  y(x + y = 10)  x  y(((x > 0)  (y  
  
  Solution
a) For every X, there exists a y such that (x+4) = y
The given statement isTRUE, since for evert integer x there exists an integer y = x + 4
b) There exists an x an y such that (x-y) = (y-x)
(x-y) = (y-x)
x = y, hence the statement is FALSE, since the value of x=y must be there for this statement
c) There exists an x for every y such that (x+y) = 10
The statement is TRUE
d) The statement is TRUE, since xor of one negative number and one positive number is always negatve

